1. Field of the Invention
The present invention relates to warning lights for emergency vehicles and the like and, particularly, to the generation of a highly conspicuous pattern of light flashes to enhance the visibility of a vehicle or other object on which a warning light assembly is mounted. More specifically, this invention is directed to a reflector drive mechanism and, especially, to an electro-mechanical drive for simultaneously imparting oscillating motion to a pair of directional warning lights. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well-suited for employment in warning light systems for emergency vehicles. Emergency vehicle warning light systems which provide an attention commanding pattern of flashing lights are well-known in the art. Such existing warning light systems employ light sources which are periodically energized, i.e., gaseous discharge tubes or incandescent lamps, mechanically driven lights or a combination of both types of directional light source. In the case of mechanically driven lights, a reflector assembly may be caused to move relative to a stationary light emitter, i.e., the reflector will be caused to rotate about an axis on which the light source is mounted, or a combination light emitter and reflector will be caused to rotate as a unit. The latter type of mechanically driven directional light source is preferred because the light emitter may be more accurately positioned relative to the focal point(s) of the reflector and thus the available light is most efficiently utilized. While full rotational motion is often highly desirable because of the 360.degree. light radiation pattern which may be obtained, rotational motion of a combination light emitter and reflector requires the added complexity of a commutator to couple direct current electrical energy between the stationary and rotating parts of the light assembly. Lights which are caused to undergo oscillatory motion do not require a commutator and thus are characterized by enhanced reliability and longer service life.
Oscillatory motion, however, presents the problem of how to generate the requisite alternate clockwise and counter-clockwise rotation of the light in an efficient and cost effective manner. Drive motor reversal, for example, can be achieved only through the use of relative complex and thus expensive electronics. Previously proposed mechanical techniques for producing changes in the rotational direction of a warning light were complex and volumetrically inefficient.
In order to obtain the ability to "cover" a full 360.degree. field of illumination, oscillating warning lights must be used in pairs. Even when the requisite field is less than 360.degree., the coupling of lights in pairs may be employed to produce a desired flash pattern and/or illumination field. Such paired operation has, in the past, required relatively complex synchronization and/or coupling mechanisms. Synchronized/coupled warning light operation has often resulted in the use of multiple drive motors, i.e., one motor per light. Also, previously available coupling mechanisms were characterized by the inability to easily adjust the relative orientations of the coupled lights.
An oscillating warning light optimally has the attributes of reliability, lack of complexity, ease of individual adjustment of a pair of coupled lights, energy efficiency, compactness and reasonable cost.